It sounds like you may be up the creek. If you are electronically inclined, open the head unit up and see if you can see anywhere on the circuit that it may have fried. It doesn't always look black, but it can once it fries. Also look for any excess water. I know it's been a few days since you washed it, but sometimes water can sit in an enclosed space for quite a while.
Either you can go that route or since you already have it out, get a 1 gallon zip lock bag, put the head unit it in, and pour some rice in around it. Don't get any in the CD or USB port, but get it around it the unit. Seal it up and let is sit for about a day, then try again. I did this with an older cell phone and it dried it out and worked like nothing happened.